Catalytic conversion of naphtha for the production of high antiknock gasoline



K. M. WATSON CATALYTIC CONVERSION OF NAPHTHA FOR THE FiIlLed Jun PRODUCTION 0F' HIGH ANTI'KNOCK GASOLINE Sept. 19, 1950 xoprm Dumm ESGQ INVENTOR KENNETH M. wATsoN BY im WM 5mm xoobm AT TORNEYS mit Patented Sept. 19, 1950 CATALYTIC CONVERSION'OFNAPHTHA FOR 'THE PRODUCTION OFHIGH ANTIKNOCK GASOLINE Kenneth Watson, Madison, Wis., assignor to Sinclair Benning Company, New York, N Y a. corporation of Maine Application June 2,7, 1947-5 Serial No. 755,642

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Mvl invention relates to. improvements in the production of aromatic hydrocarbons andl motor fuel gasolines of high anti-knock value by the catalytic conversion of naphthaA stocks of relatively high hydrogen content such as straight naphthas, thermally cracked naphthas or coke still or vis-breaker naphthas, More particularly my invention relatesv toan improvement in the catalytic hydroforrning of such naphthas. l, Ign the hydrocracking of petroleum oil stocks under destructive. hydrogenation conditions, it isy usuallyY necessary to make and supply hydro-V gen tothe system. In certain instances, tail gases are. recirculated directly inY the systern, but they etten. Contain rather lownereenteees of hvdro.n gen yor are entirely devoid of.; hydrogen,-

I, have. devised ar system for the cracking Qi nephtha. Stocks. of the type referred. ton which. the hydrogen is produced directly in thev process;

my improved process aA naphtha stoclrfis subj ected to a catalytic dehydrogenation cracking operation at approximately atmospheric pressure and in the. temperature range of from about 9.00 to 1100" F. These conditions not only plqdlle substantial proportions of hydrogen but also produce aromatic hydrocarbons in substantial ptopor-tion. The products of this cracking operation are cooled to condense out the readily con-1 densable constituents as a distillate, whichv is ex.- tracted with a selective solvent, by selective ad"l s crption or by extractive distillation for the separation of aromatic hydrocarbons, or the aro: matics are otherwise removed rorn the distillate, The remaining non-aromatic stock or other euiteble Stock, together with hydrogen prodneed thev dehvdroeenetion operation end Separated frein the condensable hydrocarbons, is subjected to a catalytic destructive. hydrogenation step at e pressure of from about, 3.0.0 to 3,000.v pornoster sonore, inch, at a Conversion temperature of. from *10.0 to 11oo r.

Y In the destructive hydrogenation step, the conf. ditions are controlled so that substantially all of the hydrogen produced in the dehvdroeenetion step is supplied to the second step invproduqng lower molecular weight hydro'genatedy cracked, or 'hydroforrned products of low boiling point and of desirable antiknock properties.` A'

The hydrogen produced in the rst part of the naphtha conversion operationI along with gaseous hydrocarbons may be used directly as separated from the readily condensable constituents, but it is preferably compressed and cooled so as to condense out the light normally gaseous hydroehrbens. present- My invention provides in the combined opera)- tionsoutlined. above several special featuresand combinations, of; steps vwhich facilitate the conversion of naphthas and the production of aromatic hydrocarbons. The invention, however, will be 4fur-ther described in connection with the single gure of theaccompanying drawing, which illustrates diagrammatically and conventionally in elevation, with par-ts broken awa (me forni of. apparatus` which may be. appropriately used torlcarrying out. my improved process.

process is illustrated inv oonneetion With the Showing in the drawing,v invhehthe Chargingy stock, for example,` aVstraight-run or cracked nenhthe of thetvne oleserloed.y is, introrlneed. into the apphlfatusthrough an inlet line 2 and forced ataeniteble-,ehersine rate and pressure by. Ineens of; e nnmn therein thr-onehe, heating oon 4. lmounted ina pipe still furnace 6. The o il in oeeeingthrongh. the eoil 4 ,is heated to a tempereture of about` 10u00? E., after which the naphtha stream. is eondneted, through a transfer line 8 intoY a catalyst chamber yill, carrying a, bed of catalyst l2`. The highly heated naphtha stock may he introntleed. either et the bottom or ton of the` catalyst chamber. A pressure of approximately. atmospheric is maintained in the chamber I to facilitate dehydrogenation of the naphtha stOCk, and the conversion of substantial pr'oportions thereofy tc aromatic hydrocarbons.

The catalyst. bed l2 may comprise a dehydron genaticn catalyst, such as chromia or molybdena on alumina,` or other suitable well known dehydrogenation and cyclicizing catalysts. Furtherricerca the catalyst may be vused in any other form, such as fluid', granular, or bead.

The. conyersion` products produced in charnber la are conducted therefrom thrOllgh a line Minto. e .eendeneer and cooler it, which is operated under conditions to condense out substantially all of the readily condensable materials. The h ydrjogen and liquidy products, together with any uncondensable hydrocarbons, are conducted into a receiver i8, in which the hydrogen and other gases are separated out and from which they are removed through a line 20.

The liquidv product inthe receiver i8l is con-l ducted through a valved line ZZ into an extractor 2h41, where the product is brought into counter` current contact with a selective solvent for aromatic hydrocarbons introduced throughY av line 2 6A and. distributed into the body of liquid in the extrarctcijL 24V at approximately the point shown. The selective solvent, together with the dissolved aromaticjhydrocarbons, move downwardly in the extractor and is discharged through a line 28 and sent to suitable equipment, not shown, for recovering the selective solvent from the aromatic hydrocarbons. The recovered solvent may then be reintroduced into the extractor 24 by the line 26. A'phenol-water system or solvent may be used, or other known solvent, for aromatic hydrocarbons. The aromatics may be separated by other means referred to above.

The non-aromatic partially-converted naphtha stock which moves toward the top of the extractor 24 is discharged therefrom through a line 30 and then picked up by a pump 32, placed under a high pressure of approximately 2,000 pounds per square inch and passed through a heating coil 34 mounted in a pipe still furnace 36. The non-aromatic charging stock in the -coil 34 is heated to a temperature preferably between v950 and 1050 F., after which it is discharged through a transfer line 38 into the upper portion of a catalyst chamber 40 which carries a bed of catalyst 42 for effecting the hydroforming of the non-aromatic partially-converted naphtha stock,

Other stocks low in hydrogen content may be cracked in the second stage of the process, instead of, or along with, the stock in the line 30, by feeding such stock to the pump 32 through a valved line 43. These stocks may be higher boiling than gasoline and typically be recycle fracf tions from conventional catalytic cracking operations consisting largely of polycyclic aromatics deficient in hydrogen and difficult to crack without the addition of hydrogen.

The catalyst 42 may comprise one 0f the typical catalysts used for hydroforming, such as the sulfides of the metals molybdenum, tungsten, iron and the like, for example. A specific metal sulfide deposited on alumina may be used as a catalyst. ,l

The hydrogen for the conversion carried out in the chamber 40 is taken directly from the rst step of the process by compressing the hydrogen containing gas in the line 20 up to a pressure in excess of 2,000 pounds per square inch, the re` sulting compressed gases being conducted directly through a valved line 44 into the top `of theA chamber 40, where they mingle with the oil products introduced through the transfer line 38. While the gases in the line 44 are rich in hydrogen, they may be further enriched by passing the gases from the compressor through a valved line to a cooler condenser 46, where at the high pres-r sure considerable proportions of any hydrocarbons present are condensed and drawn oi into a receiver 48. The greatly enriched vhydrogen containing gas is conducted from the condenser 46 through the valved line 50 directly into the top of the catalyst chamber 40. The gas inI either lines 20, 44 or 5D may be freed of olefins by con-I tact with concentrated sulfuric acid.

The mixture of hydrogen and partially converted non-aromatic material passing downward-` ly through the catalyst bed 42 are reacted together at a pressure of approximately 2,000 pounds per square inch so as to consume substantially all of the hydrogen and produce a hydrogenated cracked product comprising a high per, centage of low boiling materials of desired antiknock characteristics. The stock subjected to the conversion in chamber is already dehydrogenated and partially converted, so that in the chamber 40 there is considerable molecular breakdown of constituents boiling above the gasoline range to give hydrocarbon molecules containing a smaller number of carbon atoms. Fur- 4 thermore, considerable proportions of such hydrocarbons are cyclicized and converted to aromatics.

The reaction products at the bottom of the chamber 40, which may carry a relatively shallow or deep bed or beds of the catalyst, are conducted through a line 52 into a fractionating tower 54 where the vapors are cooled and reuxed to condense the small proportion of hydrocarbons boiling above the gasoline or motor fuel range. Such materials are discharged through a valved line 56.

The motor fuel vapors and the gases are discharged from the tower 54 through a line 58, condensed in a condenser 60 and recovered in a receiver 62. The product is withdrawn from the receiver through a valved line 64, while the normally gaseous hydrocarbons, including hydrogen, are withdrawn through a valved line 56. The desired reflux ratio is maintained on the tower 54 by returning a part of the condensate from the condenser 60 through a valved return line 68,

In my process the naphtha stock either for the first or second cracking zones may be heated in any other manner than that described above, and the stock may be contacted with the catalyst either in countercurrent or concurrent flow, and in either cracking rone the catalyst may be one of the fluid type, a bead type catalyst or a granular catalyst, or in the form of an aerogel. Itis generally understood how these different forms of catalysts are employed in conversion operations, and therefore that procedure need not be delscribed in detail. If catalyst chambers such as I0 and 40 are employed, they may be operated in duplicate or triplicate, so that the catalyst bed of one chamber may be regenerated while another chamber is being used to carry out the conversion operation.

The non-aromatic naphtha stock, recovered from the extractor 24 and used as the charging stock in the second cracking zone, is preferably handled so that a very large percentage of it is converted to high anti-knock constituents within the gasoline boiling range. Constituents of boiling points intermediate between the gasoline pr" duced in the second stage and the heaviest fractions withdrawn through line 56 are advanta-y geously recycled for retreatment in the second stage by withdrawing a side-stream from tower 54 and returning it to the suction of pump 32 by means of a line not shown.

The conditions employed in the second conversion Zone in chamber 40 are preferably such that substantially all of the hydrogen introduced thereinto from the rst conversion zone is free to enter into the hydroforrning reactions, and therefore the hydrogen introduced into the chamber 40 is preferably free of olens which would take up hydrogen. However, a portion or all of the gases, including hydrogen, discharged through the line 66 are advantageously recycled to the top of the reaction chamber 40 to augment the hy# drogen ratio and further the hydroforming re: actions therein, the gases being drawn from the line 66 .by a compressor in a line 10, discharging into the line 20 beyond the compressor therein.

The operation in the dehydrogenation zoneis correlated with that in the hydrocracking zone so that adequate hydrogen is produced for the hydrocracking reactions.

The aromatic hydrocarbons recovered in the extractor 24 may be blended with the product recovered in receiver 62 so as to increase'the octane value and power factor of the gasoline product. On the other hand, the aromatics from the extractor `24 may be fractionated and used for various other purposes as desired. The liquid product recovered in the receiver 4'8, which is at a pressure higher than that employed in the chamber 40, may be fractionated to recover the various individual or groups of hydrocarbons.

I claim:

In the production of high anti-knock gasoline by the catalytic conversion of naphthas in the presence of hydrogen, the improvement which comprises contacting a naphtha of relatively high hydrogen content with a dehydrogenaton catalyst at a temperature of from 900 to 1100D F. in a first cracking zone in Which a pressure of approximately atmospheric is maintained, producing substantial proportions of aromatic hydrocarbons and hydrogen in said zone, continuously removing the hydrogen and products of conversion from said zone, separating o-ut the hydrogen substantially free of hydrocarbons, separating the aromatic hydrocarbons from the con- Verted naphtha stock to provide a substantially non-aromatic cracked naphtha stock, subjecting such naphtha stock While substantially free from aromatic hydrocarbons to cra-cking conditions in a second cracking zone in a continuous operation in the presence of the hydrogen produced by 'the dehydrogenation in said rst Zone by contacting the non-aromatic stock and hydrogen with a hydrogenating cracking catalyst at a temperature of from 700 to 11.00 F. and a pressure of from 300 to 3,000 pounds per square inch, introducing a cracking stock difficult to crack and deficient in hydrogen into the second cracking zone in addition to the non-aromatic stock from the rst zone, and recovering a high anti-knock gasoline product from the cracking of the non-aromatic stock and the additional cracking stock in the presence of hydrogen.

KENNETH M. VATSON.

REFERENCES CITED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS Number Namev Date 2,202,401 Rosen May 28, 1940 2,241,430 Snow May 13, 1941 2,289,716 Marschner July 14, 1942 2,292,677 Thomas Apr. 11, 1942 2,389,176 Anderson Nov. 20, 1945 2,407,492 Hall et al Sept. 10, 1946 

